This invention relates to dentistry, and more particularly to apparatus utilized for building a superstructure on broken or undermined dentition.
Where a portion of tooth is broken, decayed or the like, one dental technique is to remove the decayed or broken portion of the dentition so as to define a tooth understructure. A number of channels are then drilled in the understructure and rods are threaded into these channels with a portion of the rods projecting above the surface of the understructure. A superstructure is then built on this surface so as to adhere onto the portion of the rods extending above the understructure. This method is described in detail in my U.S. Pat. No. 3,434,209.
The particular metal rods or dental anchors which are utilized to interconnect the superstructure and anchor it onto the understructure, have been of various types. For example, in my U.S. Pat. No. 3,675,328, there is described a dental anchor having a plurality of threaded sections with each section being capable of being severed apart from the other. In my U.S. Pat. No. 3,675,329, there is provided an anchoring pin with a head, wherein the head extends above the understructure so as to be received in the superstructure and provide a displacement-resisting portion in the superstructure. A further dental anchor is provided in my U.S. Pat. No. 4,053,982, which utilizes an L-shaped manipulating portion which can be received in a dental tool for manipulating the anchor into the understructure. Various types of manipulating portions can also be provided on the dental anchor, as shown in my U.S. Pat. No. 4,202,101, which also describes a hand held driver for use in inserting the dental anchor in the understructure.
Although each of these prior art metal dental anchors and related apparatus have been exceedingly useful, specific problems have been noted when using this dental technique. One problem concerns the cracking of the understructure as the dental anchor is being threaded into it. Typically, the channel is provided in the understructure and the anchor is then threaded into that channel. In most cases, a self-threading arrangement is provided on the dental anchor, so that the insertion of the anchor in the channel self-threads into the understructure. During this threading, and typically upon reaching the bottom of the channel, cracks can form in the understructure.
Another problem is the suitable retention of the superstructure firmly in position on the understructure. The technique must include a provision for preventing rotation or displacement of the superstructure with respect to the understructure. In the various prior art arrangements, it has been provided to retain part of the threaded portion of the anchor projecting above the understructure to retain the superstructure. Additionally, an enlarged head has been provided on the threaded portion of the anchor for embedding in the superstructure.
Also, by inclining the anchors in the understructure, the angled arrangement provides additional adhesion within the superstructure. It is also possible to bend over a portion of the threaded anchor above the understructure so as to provide additional retention within the superstructure and thus provide a further displacement resistant accommodation.
Nevertheless, further improvement would be desired in retaining the superstructure in place and avoiding displacement of the superstructure after it has been secured onto the understructure.